Abstract

Decrease or growth of population comes from the interplay of death and birth (and locally, migration). We revive the logistic model, which was tested and found wanting in early-20th-century studies of aggregate human populations, and apply it instead to life expectancy (death) and fertility (birth). For death, once an individual has legally entered society, the logistic model portrays the situation crisply. Human life expectancy is reaching the culmination of a 200-year process that forestalls death until about 80 for men and the mid-80s for women. No breakthroughs in longevity are in sight unless genetic engineering comes to help. For birth, the logistic model covers quantitatively its actual morphology. However, because we have not been able to model this essential parameter in a predictive way over long periods, we cannot say whether the future of human demographics is runaway growth or slow implosion. Thus, we revisit the logistic analysis of aggregate human numbers.